I could say the same to you regarding it being 'not so hard to understand'. I'm not disputing that he's being paid and earning a living. The point I'm arguing, is that legally it could be very difficult if they decided to stop him from doing IPL or any other tournament. The fact they're paying him wouldn't be a defence - because you're allowed to have other jobs and make other wages. That's not just in cricket, that's in everyday life.
The crux of it again, is, that if FTECB rejected his request to play in these tournaments - thus preventing him from earning (more) money, they would likely be in breach of employment law, or atleast his human right to work.
Even if they've got it written into his contract that they have any say on when and where he plays cricket - the Stokes camp could still make it very awkward for FTECB if they wanted to. It's one thing for them to stop him playing IPL if England need him to be fit and to play for them, but considering they've made it clear he won't be playing for them, he must be allowed to earn money elsewhere if he so wishes.
That's kind of what I'm getting at. There's no minefield at present because FTECB are allowing him the freedom to play cricket when and where he wants (just not for them). The fact they're still paying him his England wage gets them out of any potential hot water over denying him his human right to work - as it would with any employer.
We'd see tribunals and court cases all over the place if companies suspended people without pay, en masse, everytime they had something to answer. However, that's the whole reason people are placed on 'gardening leave', they remain on full pay and so that satisfies any legal issues regarding punishment before trial and innocent until proven guilty.